I have a 2003 Excursion Limited 4x4 with the 7.3. Bought the 2003 b/c it's the last year of the 7.3. It has 95k on it, gets close to 20 mpg on the interstate, and about 17 city/highway. It's pretty much stock, but the Michelins are a tad larger than the factory tires and I do have the Bullydawg controller (set on tow/mpg).
I pulled out the third seat and put a thick liner in the back. I haul just about anything back there, including engines and trannies. Not as easy to unload as a pickup, but it works quite well for me.
It tows very nicely. I have a car trailer, have made several cross country trips hauling cars and parts, and have never had any issues. I get 18 mpg towing on the interstate.
It hasn't been trouble free, but nothing too expensive yet.
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